In certain situations the mass or the concentration of a substance that is present in a patient's body has to be checked or monitored—e.g., by the physician in charge—be it for diagnostic reasons only or because the patient's state needs to be actively controlled by amending either concentration or mass of the substance. Hemoglobin (Hb) is such a substance among many others.
In practice, the concentration of hemoglobin (Hb, also known as Hgb, being the iron-containing oxygen-transport metalloprotein in the red blood cells) is measured by means of blood samples to assess the anemia state of the patient. Values below given thresholds are usually considered as a sign for the manifestation of “anemia” being defined as a decrease in normal number of red blood cells (RBCs) or less than the normal quantity of hemoglobin in the blood.